In the publication U.S. Pat. No. 5,147,386 there is described a joint prosthesis having two screw-like members which are mounted or attached to the respective bones to be connected by the prosthesis. The joint consists of a socket and a head, whereby the end of the head member is attached to one of the screw-like members by a press fit. To secure the screw-like members by screwing, there are grooves for a screw tool in outer end surfaces thereof, which means that the grooves will form sharp edges that might harm adjacent tissue, which of course is utterly inappropriate.